1. Field of the Invention
The present invention relates to a heat sink and a protective cover for a tape automated bonding ("TAB") integrated circuit mounted onto a printed circuit board. Furthermore, the present invention relates to a method and apparatus for dissipating heat generated by a TAB integrated circuit mounted on a printed circuit board.
2. Art Background
The high speed and high power integrated circuits created today generate significant amounts of heat. The heat generated inside of an integrated circuit must be efficiently transferred away from the integrated circuit and dissipated. If the heat is not dissipated the circuit's performance will degrade, or, worse, the circuit might overheat and malfunction.
A simple and effective way to dissipate the heat generated by an integrated circuit is to attach a heat sink to the integrated circuit package. A heat sink is a piece of heat conductive material having a large surface area. Since the heat sink conducts heat well, it draws the heat away from the integrated circuit and spreads it throughout the body of the heat sink. The large surface area of the heat sink then distributes the heat to the surrounding air which carries it away. The efficiency of a heat sink can be improved by adding a fan to the system to circulate the air, thereby improving the process of transferring heat from the heat sink to the surrounding air.
A Pin Grid Array ("PGA") style integrated circuit package consists of a rectangular plastic or ceramic package with a plurality of pins protruding from the bottom of the package. PGA integrated circuits are often inserted into PGA sockets which are mounted onto a printed circuit board. Alternatively a PGA integrated circuit can be mounted directly onto a printed circuit board.
To efficiently cool a high wattage PGA integrated circuit, a heat sink can simply be clipped on to the PGA integrated circuit. Examples of this device are illustrated in FIG. 1a and FIG. 1b and are manufactured by International Electronic Research Corporation of Burbank, Calif. Referring to FIG. 1a, a heat sink 1 is attached to a PGA integrated circuit 11 using a spring clip 7. The spring clip 7 clips into the gap between the PGA integrated circuit 11 and the PGA socket 13. Referring to FIG. 1b, a heat sink 1 is attached to the PGA integrated circuit 11, which is mounted directly onto a printed circuit board 10. In the arrangement of FIG. 1b, the spring clip 7 clips into the gap between the PGA integrated circuit 11 and the printed circuit board 10.
The technique of clipping a heat sink onto an integrated circuit, however, does not work for chips mounted in TAB (tape automated bonding) integrated circuits packages. TAB integrated circuit packaging is a relatively new form of integrated circuit packaging which reduces the size of the integrated circuit package and increases the number of leads.
The reason that heat sinks cannot be clipped onto TAB integrated circuit packages is that TAB integrated circuit packages are usually directly attached to the printed circuit board. This is illustrated in FIG. 1c. Referring to FIG. 1c, a TAB integrated circuit 5 is shown directly attached to a printed circuit board 10. As can be seen at the contact point 7 where the TAB integrated circuit 5 and the printed circuit board 10 meet, there is no gap where a spring clip could clip onto and attach a heat sink.
Although TAB integrated circuits tend to be smaller than PGA integrated circuits, TAB integrated circuits typically incur bigger problems releasing thermal energy efficiently. This is due to the smaller leads and the smaller package size of TAB integrated circuits, which decrease the ability to dissipate heat.